JP2009203911A - Pump or water turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate reduction in efficiency as an engine, by enabling air existing in a shaft case from smoothly slipping out in response to a start of operation, in a pump or a water turbine. <P>SOLUTION: This water turbine comprises an impeller 14 capable of driven rotation by lowering energy of water, a casing C for enveloping this impeller 14, a rotary shaft 12 equipped with the impeller 14 in an integrally rotatable state, and the shaft case 13 for rotatably surrounding the rotary shaft 12 in a state of being installed in the casing C, and is provided with an air exhaust means H having an opening part 20a opening on the lower end of the rotary shaft 12, forming an air bleeding passage L communicating with the inside of the shaft case 13 in a hollow shape in the rotary shaft 12, communicating with the air bleeding passage L from the opening part 20a and openable in the external atmosphere. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pump or a water wheel, and more particularly to a technique for efficiently removing air inside a shaft case that supports a rotating shaft of an impeller.

  In general, a pump or a water wheel is composed of an impeller capable of being driven to rotate by a pumping action or a liquid flow, a casing surrounding the impeller, a rotating shaft equipped with the impeller in an integrally rotating state, and a casing. And a pump case disclosed in Patent Document 1 and a pump disclosed in Patent Document 2 are known.

  In the axial water turbine of the hydroelectric generator disclosed in Patent Document 1, the impeller (5) rotating shaft (6) is also the rotating shaft of the generator (3), and the inner side of the turbine casing (2) A shaft case (not shown) surrounding the mechanical seal (9) is provided below the peripheral cylinder (2B) (see FIG. 1 and the like). The mixed flow pump disclosed in Patent Document 2 is equipped with a shaft case (16) called a cone that supports the bearing (14) of the rotating shaft (6) of the impeller (2, 3). (See FIG. 3 etc.).

  In any pump or water wheel shown in any patent document, air (air) is initially contained in the inner space of the shaft case, and the root part of the impeller is used when the pump or water wheel is in operation. It is considered that the water gradually enters the water-filled state by gradually expelling air from the gap of the shaft case and being submerged. However, since the bearings and mechanical seals housed in the shaft case perform the desired performance under the condition that liquid such as water exists around them, the actual operation from the start of the operation of the pump or the water turbine There is a problem that sufficient bearing function and seal function are hardly exhibited until water is filled.

Further, in the water turbine disclosed in Patent Document 1 and the like, a large number of bubbles are generated in the casing surrounding the impeller from the start of operation, and thus there is a problem that the water flow is limited and power generation efficiency is reduced. . That is, in the vertical shaft flow turbine, the extrusion of air by the water flow tends to be incomplete inside the casing, and the rotation of the impeller starts in a mixed state of water and air, and the air rises. It is considered that the air tends to stay in the casing as a result of the fact that the water flows from the top to the bottom while trying to escape and the air does not readily escape.
JP 2003-065199 A Japanese Patent Laid-Open No. 10-184589

  An object of the present invention is to eliminate the reduction in the efficiency of the engine by allowing the air present in the shaft case to smoothly escape with the start of operation in the pump or the water turbine having the above-described configuration. Also, in a vertical shaft type water turbine in which the moving direction of air (upward) and the moving direction of liquid such as water (downward) are opposite in the casing surrounding the impeller, the air in the casing is efficiently used. The purpose is to make it easy to leave.

The invention according to claim 1 is equipped with an impeller 14 capable of being driven to rotate by a pumping action or a liquid flow, a casing C surrounding the impeller 14, and the impeller 14 in an integrally rotated state. A pump or a water turbine having a rotating shaft 12 and a shaft case 13 that rotatably surrounds the rotating shaft 12 in a state of being housed in the casing C.
The rotary shaft 12 has an opening 20a that opens at one end of the rotary shaft 12, and an air vent path L that communicates with the inside of the shaft case 13 is formed in the rotary shaft 12. The opening 20a An air discharge means H is provided which communicates with the air vent path L and can be opened to the outside atmosphere.

  According to a second aspect of the present invention, in the pump or the water turbine according to the first aspect, one end side of the rotary shaft 12 having the opening is rotatably supported by the casing C in a sealed state. It is what.

  According to a third aspect of the present invention, in the pump or the water turbine according to the first or second aspect, the shaft case 13 has a communication hole 24 communicating with the liquid flow path R surrounded by the shaft case 13 and the casing C. It is characterized by being formed.

According to a fourth aspect of the present invention, in the pump or the water wheel according to any one of the first to third aspects, the casing C houses the mixed flow impeller 14 and is guided to the upper side of the mixed flow impeller 14. A water turbine casing in which the water pipe 8 is disposed, or a pump casing that houses the mixed flow impeller 14 and has a pumping pipe on the upper side of the mixed flow impeller 14;
The air vent path L opens at the lower end of the rotary shaft 12 facing upward and downward, and opens into the shaft case 13 along the axial center P of the rotary shaft 12 and communicates with the vertical hole 20. And a radial hole 26.

The invention according to claim 5 is the water turbine according to claim 3, wherein the casing C accommodates the mixed flow impeller 14 and the water guide pipe 8 is disposed on the upper side of the mixed flow impeller 14. Configured,
The rotating shaft 12 is configured to have a vertical axis P, and the communication hole 24 is located at a height level position at or near the slow flow portion Ra having the largest cross-sectional area in the liquid flow path R. It is characterized by being formed.

  The invention according to claim 6 is characterized in that, in the water turbine according to claim 5, the generator 3 that is interlockedly connected to the upper end portion of the rotary shaft 12 is provided.

  According to the first aspect of the present invention, attention is paid to the structure in which the rotating shaft that supports the impeller passes through the shaft case, and the air vent passage formed hollow in the rotating shaft and the air discharge means communicating therewith are used. Since the inner space of the shaft case and the outside (outside the machine) communicate with each other, the air present in the shaft case can be pushed out and discharged by water pressure generated by pumping (pump) or gravity (water wheel). In other words, it is possible to smoothly remove the air inside the shaft case by using a rational means that uses the originally equipped rotary shaft and eliminates the need for a drive source. It is possible to provide a pump or a water turbine in which the reduction in efficiency as an engine is eliminated by allowing the air present in the shaft case to smoothly escape with the start of operation.

  According to the invention of claim 2, since one end side of the rotating shaft having the opening is rotatable and is supported by the casing in a sealed state, the originally equipped rotating shaft is extended to the inside thereof. It is relatively easy to install an air vent path, requires almost no new space, does not require a dedicated rotating shaft bearing, and constructs a rational means that eliminates the need for a drive source for air discharge. can do. By the rational means, the air inside the shaft case can be smoothly extracted, and the pump or the water turbine in which the effect according to the invention of claim 1 is enhanced can be provided.

  According to the invention of claim 3, the air present in the liquid flow path can be moved into the shaft case through the communication hole by the pressure of water, and therefore the air inside the shaft case and the liquid Air entering from the flow path gathers in the internal space of the shaft case, and the collected air can be discharged to the outside through the air vent path. As a result, both the air present in the shaft case and the air present in the liquid flow path are smoothly discharged with the start of operation, and a more excellent pump or water turbine that eliminates the reduction in efficiency as an engine is obtained. Can be provided.

  According to the invention of claim 4, the air vent path formed hollow in the rotating shaft has a structure that is easy to work with, such as a vertical hole and a radial hole along the axis of the rotating shaft, and has a good productivity. Any one of the above-described effects according to the inventions of Items 1 to 3 has an advantage that it is exhibited in a vertical shaft type pump or water turbine whose rotating shaft is directed in the vertical direction.

  According to the invention of claim 5, although described in detail in the section of the embodiment, the following effects can be obtained. That is, air that moves upward due to buoyancy and water that moves downward due to gravity are reversed, and foaming is activated in a slow flow portion where the cross-sectional area is maximum. The air present in the shaft can easily enter the shaft case through the communication hole. Therefore, the air inside the shaft case and the air entering from the liquid flow path float and gather at the top in the inner space of the shaft case, and the collected air is now passed through the air vent and the air discharge means to the outside. It becomes possible to discharge. In other words, a relatively simple and new space is almost unnecessary to provide an air vent path inside the vertical rotation shaft that is originally installed, and a drive source for discharging air is also unnecessary. By rational means, the air inside the shaft case and the air staying in the casing can be extracted smoothly, and the state where the vertical shaft type water turbine operates efficiently can be maintained.

  As a result, in the vertical shaft water turbine in which the direction in which air escapes (up) and the direction in which liquid such as water moves (down) are opposite to each other inside the casing surrounding the impeller, the air in the casing is removed. It can be efficiently removed. In this case, if a generator linked to the upper end of the rotating shaft is provided as in claim 6, it is possible to construct a power generator that operates efficiently over a long period of time.

  Embodiments of a pump or a water turbine according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a power generator, FIG. 2 is a cross-sectional view showing the main structure of a vertical-shaft diagonal flow turbine, FIG. 3 is a cross-sectional view showing the state of air escape during operation of a water turbine, and FIG. It is the schematic which shows the air vent structure in.

[Example 1]
Example 1 of a pump or a water turbine is a vertical axis diagonal water turbine S in a power generator E as shown in FIG. The power generation device E has a structure in which the vertical shaft diagonal flow turbine S is rotated using the water taken from the dam lake 1 and flows into the river 2 below, and thereby the generator 3 is rotated to generate power. An inlet valve 4, which is an on-off valve that is switched by a driving mechanism 4a, etc., a vertical-shaft diagonal water turbine S, a discharge pipe 6, a generator 3, and the like.

  As shown in FIGS. 1 and 2, the vertical-shaft diagonal water turbine S includes a water guide pipe 8 connected to a water intake pipe 7, an impeller case 9, an outlet case (bell mouth) 10, an outlet elbow pipe 5, and the like. Although it is omitted in FIG. 1, it is installed in a minimal space along the outer surface of the lake wall 1A of the dam lake 1 (in short, it is installed almost in contact with the lake wall 1A) Many). The water guide pipe 8 includes an elbow part 8a connected to the water intake pipe 7, an upper projecting pipe part 8b for installing the generator 3, a straight tubular water guide main part 8c, and a downwardly expanding connection pipe part 8d. A rotating shaft 12 that is rotatably supported by a plurality of bearings 11 on the inner shaft center P is housed. The upper end of the rotating shaft 12 is interlocked with a main shaft (not shown) of the generator 3.

  In the vicinity of the height position corresponding to the outlet case 10 of the rotating shaft 12, an impeller 14 having a plurality of blade portions 14a located inside the outlet case 10 has its hub portion 14b and is fitted in an integrally rotated state. The shaft case 13 that is liquid-tightly connected to the hub portion 14b is provided with a bearing portion 15 for the rotating shaft 12. The upper end of the outlet elbow pipe 5 is connected to the lower end of the outlet case 10. The impeller 14 is configured as an assembly type in which a plurality of blade portions 14a are connected and integrated with the hub portion 14b by bolting, but may be integrated.

  The shaft case 13 is formed on the main casing 13A in a state where the shaft case 13A is integrally formed with the impeller case 9 via the plurality of continuous ribs 15 and the plurality of guide blades 16 and is located inside the connecting pipe portion 8d. It is comprised by the upper case part 13B connected and integrated liquid-tightly. The connecting pipe portion 8d and the upper end portion of the impeller case 9 and the shaft case 13 form a downwardly expanding annular expansion flow path 17, and the lower portion of the impeller case 9 and the lower portion of the shaft case 13 form the blade portion. A constricted annular channel 18 is formed following the constricted annular shape 14a. A liquid channel R is formed from the expanded channel 17 and the narrowed channel 18. The rotating shaft 12 is penetrated through the top of the upper case portion 13B having a substantially conical cylindrical shape.

  The lower end portion (one end side) of the rotary shaft 12 is a shaft that is rotatably supported by a take-out convex portion 5A that protrudes downward from the outlet elbow pipe 5 via a bearing portion 19 and a sealing means 27, and is supported in a sealed state. In addition to being formed at the end 12 a, the rotary shaft 12 is formed with a central vertical hole 20 that is open at the lower end and reaches the lower portion of the water conduit 8, centering on the axis P. A discharge path 22 made of a tube material, a pipe material, or the like is connected to the lower end of the central vertical hole 20 via a lid (an example of an outer wall portion) 21 of the extraction convex portion 5A. Is connected. Although the example using the central vertical hole 20 opened at the lower end of the rotating shaft 12 is shown in the above embodiment, the present invention is not limited to this, and the lower end opening of the rotating shaft provided with the central vertical hole is closed with a plate material or the like. You may make it open by providing a radial horizontal hole in the lower end side of a shaft, and you may make it vent air from two places at the upper and lower ends of a shaft. Incidentally, reference numeral 23a in FIG. 2 denotes a valve switching operation means such as a motor.

  As shown in FIGS. 2 and 3, a short straight body case portion 13 </ b> C positioned between the upper and lower sides of the connecting rib 15 and the guide blade 16 in the shaft case 13 has a plurality of predetermined angles in the circumferential direction with respect to the shaft center P. The communication holes 24 are formed at the locations, and the horizontal holes (radial holes) 26 that communicate with the inner space 25 and the central vertical hole 20 are located at the upper end portion in the inner space 25 of the shaft case 13. And, it is formed at a plurality of locations so as to be radial with respect to the axis P. The central vertical hole 20 and the horizontal hole 26 constitute an air vent path L. Note that reference numeral 28 shown in FIG. 2 denotes a viewing window for visually recognizing the internal state of the connecting pipe portion 8. Further, the lateral holes (radial holes) 26 do not have to be in two upper and lower rows, and may be one row or three or more rows. Next, how the air escapes when the water turbine S is operated will be described.

  FIG. 3 shows a situation in the vicinity of the impeller 14 when water is passed through the water wheel S. That is, the inlet valve 7 is switched from “closed” to “open” and the water stored in the dam lake 1 flows into the vertical-shaft diagonal flow turbine S and the generator 3 is rotated to generate power. The situation is such that air and inflowing water are mixed in at the cross-sectional shape changing portion extending from the connecting pipe portion 8d to the impeller 14 site. In FIG. 3, the white arrow indicates the flow of water, and the solid arrow indicates the flow of air. The water descending vigorously from the intake pipe 7 is a location before the cross-sectional area of the flow path changes from the maximum to a decreasing tendency, and the flow velocity is the slowest, that is, the diameter of the liquid flow path R is the largest. Large impeller case (an example of a slow flow portion) 9 has a tendency that foaming becomes active (air easily collects) particularly at the maximum diameter portion Ra. Therefore, the communication hole 24 is provided at the place (its height level). By providing, it becomes possible to efficiently move the air present in the liquid flow path R to the internal space 25 of the shaft case 13.

  It is considered that the air that is going to move upward by buoyancy moves against the water flowing from top to bottom by gravity, and foaming is most active in the straight body case portion 13C, which is the starting point where the cross-sectional area narrows. The air that cannot be moved is pushed into the shaft case 13 from the plurality of communication holes 24 formed in the straight body case portion 13C by the pressure of water. The inside of the shaft case 13 is also in a state where water entering from each gap portion gradually accumulates as shown in FIG. 3 from the state of only air, and the air that was originally inside the shaft case 13 The air coming from the liquid flow path R floats and gathers at the top in the internal space 25 of the shaft case 13, and the collected air passes through the horizontal hole 26 and the central vertical hole 20, that is, the air vent path L. Can be discharged to the outside.

  Therefore, if the on-off valve 23 is operated to “open”, the air present in the inner space 25 of the shaft case 13 and the air present in the liquid flow path R are rotated by the pressure of the water flowing down in the casing C. 12 can be discharged out of the apparatus through an air vent L formed in the apparatus 12. When what is discharged from the outlet (not shown) of the on-off valve 23 starts to change from air to water, the on-off valve 23 may be operated to “close” on the assumption that the air in the liquid flow path R and the shaft case 13 has been completely removed. Conceivable. Further, since it is conceivable that a mixture of air and water is discharged from the on-off valve 23 for a while, the on-off valve 23 is closed after a predetermined time has elapsed since the start of discharging the mixture of air and water. You may do it. The on-off valve 23 may be an exhaust valve using a float.

  That is, the vertical axis mixed-flow turbine S includes a mixed flow impeller 14 that can be driven and rotated by water falling through the water conduit 8, a casing C that surrounds the mixed flow impeller 14, and the impeller 14. A shaft that forms a liquid flow path R between the rotating shaft 12 equipped in an integrally rotating state and the casing C (the impeller case 9) that rotatably surrounds the rotating shaft 12 in a state of being housed in the casing C. And an air vent path L that has an opening 20 a that opens at the lower end (an example of “one end side”) of the rotating shaft 12 and communicates with the inside of the shaft case 13. Is formed hollow in the rotating shaft 12, communicates with the air vent path L through the opening 20a, and is composed of a discharge path 22 and an on-off valve 23 so as to be openable to the outside atmosphere. H is provided. One end of the rotary shaft 12 is rotatably supported by a take-out convex portion 5A that protrudes outward from the casing C via a bearing portion 19 and in a sealed state via a sealing means 27, and air discharge The means H is configured to have a discharge hole 21a that is formed through the lid 21 that is the outer wall portion of the take-out convex portion 5A in a state of facing the opening 20a. “At least one end side of the rotating shaft” means “at least one of the one end side and the other end side of the rotating shaft”.

  The casing C is configured as a water turbine casing in which the mixed flow impeller 14 is accommodated and the water guide pipe 8 is disposed on the upper side of the mixed flow impeller 14, and the air vent path L is a lower end of the vertical rotating shaft 12. And has a vertical hole 20 that extends along the axis P of the rotary shaft 12 and a radial hole 26 that opens inside the shaft case 13 and communicates with the vertical hole 20. The communication hole 24 is formed at a height level position at or near the connecting pipe portion (an example of a large diameter portion) 8d having the largest diameter in the liquid flow path R.

  In this way, by examining the movement of air and water in the internal space 25 of the shaft case 13 and the liquid flow path R, it is necessary to provide the take-out convex portion 5A of the discharge elbow pipe 5 and the on-off valve 23. The rotary shaft 12 that is installed is extended and a new space that is relatively simple, such as providing an air vent path L therein, is almost unnecessary, and a drive source for discharging air is also unnecessary. By rational means, the air in the shaft case 13 and the air staying in the casing C can be smoothly removed, and the state in which the vertical-shaft diagonal water turbine S operates efficiently can be maintained. . Thereby, it is possible to rotate the generator 3 efficiently over a long period of time and to operate the power generator E stably.

  By the way, as shown by a virtual line in FIG. 1, it is conceivable to provide the on-off valve 4 in the middle of the discharge pipe 6 instead of the intake pipe 7. With this structure, the intake pipe 7 and the casing C are always filled with water, and the inconvenience due to a mixture of air and water at the start of operation as the water turbine S (in the shaft case 13 and the liquid) It is preferable that air does not easily escape from the flow path R) structurally. However, in order to provide the on-off valve 4 on the downstream side of the water turbine S, it is attached to the discharge pipe 6 which is a buried pipe buried in the soil, so a large-scale civil engineering work is required, and the cost and construction period are increased. In addition, there are many cases where the buried portion of the discharge pipe 6 cannot or cannot be provided with other devices such as an on-off valve (such as a concrete bank shown in FIG. 3).

  Therefore, the on-off valve 4 is often provided as an inlet valve in the intake pipe 7. At that time, the inconvenience of “it is difficult for air to escape” becomes a new problem. However, the structure in which the rotary shaft 12 is extended downward and the air is exhausted through the rotary shaft 12 can solve the problem with less economic disadvantage. It has become. Although there is an idea of installing an air vent pipe outside the casing C, the superiority of the vertical-shaft diagonal water turbine characterized in that it can be installed in a place with a narrower planar space is not preferable. In the above embodiment, an example of a vertical-shaft mixed-flow turbine has been described. However, a vertical-shaft mixed-flow pump may be used.

[Example 2]
As shown in FIG. 4, the second embodiment of the pump or the water wheel can be pumped to the liquid by being accommodated in the pump casing C in which the suction pipe 31 is arranged on the upstream side of the mixed flow impeller 14 and the impeller case 32. This is a horizontal shaft pump A having a rotary impeller 14, a rotary shaft 12 equipped with the impeller 14, a drive source 33 such as an electric motor for driving and rotating the rotary shaft 12. The tip end portion 12a of the rotary shaft 12 that passes through the hub portion 14b of the impeller 14 is rotatably supported by the shaft case 13 that is supported inside the impeller case portion 32 via the rib portion 32a.

  A single rotating shaft 12 that also serves as a motor shaft is formed with a hollow central horizontal hole 20 (corresponding to the air vent path L) penetrating from the tip (an example of one end side) to the base end (the other end). The air discharge means H including the discharge path 22 and the on-off valve 23 is formed so that the air in the internal space 25 of the shaft case 13 can be discharged to the outside. On the proximal end side of the rotary shaft 12 that is rotatably supported by the take-out convex portion 5A, an open / close valve 23 that can be opened and closed by a discharge path 22 and valve switching operation means 23a is connected. The air discharge means H is configured to have a discharge hole 21a formed so as to penetrate the outer wall portion 21 of the extraction convex portion 5A in a state of facing the opening 20a.

  In this horizontal shaft pump A, water infiltrates into the internal space 25 of the shaft case 13 from a gap portion (an example of a communication hole) 24 due to the pressure of water pumped by driving and rotating the impeller 14. The air existing in the internal space 25 (particularly, the air having a volume lower than the axis of the rotary shaft 12) is pushed from the opening 20a at the tip of the rotary shaft 12 to the central lateral hole 20, and the discharge path 22 and It can be discharged out of the machine through the on-off valve 23.

[Another Example]
Although not shown (see FIG. 2), for example, a fixed pipe standing from the discharge elbow pipe 5 is relatively rotatable at the tip of the rotary shaft 12 having a length ending up to the impeller 14 and is sealed. A structure in which the air in the shaft case 13 connected in a state and passing through the central vertical hole 20 is discharged from the outlet of the hollow path of the fixed pipe is also possible. In this case, it is not necessary to extend the rotating shaft 12 downward as in the first embodiment. In addition, although the said Example demonstrated the fluid machine provided with a mixed flow blade | wing, it is not limited to this, For example, this is applied to various types of vertical shaft type pumps and horizontal shaft type water turbines provided with an axial flow blade. It is also possible to apply the invention. Moreover, although the example which uses a discharge path and an on-off valve as an air discharge | emission means was shown, it is not limited to this, You may not provide an on-off valve only by a discharge path, and forcibly A configuration in which a fan or a pump for discharging air is attached may be used.

Schematic diagram showing the schematic structure of a power generator using a vertical-shaft diagonal turbine (Example 1) Sectional drawing which shows the detailed structure of the casing vicinity in the water turbine of FIG. Cross-sectional view of the casing Casing in horizontal axis pump and sectional drawing of the vicinity (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Generator 8 Water guide pipe 9 Slow flow part 12 Rotating shaft 13 Shaft case 14 Impeller 20 Vertical hole 20a Opening part 24 Communication hole 26 Radial direction hole 31 Suction pipe C Casing H Air discharge means L Air vent path P Shaft center R Liquid flow Road

Claims (6)

Impeller capable of being driven to rotate by pumping action or liquid flow to liquid, casing surrounding the impeller, rotating shaft equipped with the impeller in an integrally rotating state, and a state in which the casing is installed A shaft case rotatably surrounding the rotating shaft, and a pump or a water wheel,
An air vent path having at least one opening on the one end side of the rotating shaft and communicating with the inside of the shaft case is formed hollow in the rotating shaft, and the air vent path is formed through the opening. And a pump or water turbine provided with air discharge means that can be opened to the outside atmosphere.   The pump or the water turbine according to claim 1, wherein one end side of the rotating shaft having an opening is rotatably supported by the casing in a sealed state.   The pump or water wheel according to claim 1 or 2, wherein a communication hole is formed in the shaft case so as to communicate with a liquid flow path surrounded by the shaft case and the casing. The casing contains a mixed flow impeller and a water turbine casing in which a water guide pipe is disposed on the upper side of the mixed flow impeller, or contains a mixed flow impeller and a pump pipe on the upper side of the mixed flow impeller. Configured as a pump casing,
The air vent path has a vertical hole that opens at a lower end of the rotary shaft that is vertically oriented and extends along the axis of the rotary shaft, and a radial hole that opens inside the shaft case and communicates with the vertical hole. The pump or the water wheel according to any one of claims 1 to 3, which is configured as described above. The casing is configured as a turbine casing that houses a mixed flow impeller and a conduit pipe is disposed on the upper side of the mixed flow impeller.
The rotary shaft is configured to have a vertical axis, and the communication hole is formed at a position of a height level at or near the slow flow portion having the largest cross-sectional area in the liquid channel. Item 4. The water wheel according to item 3.   The water turbine according to claim 5, further comprising a generator that is interlocked and connected to an upper end portion of the rotating shaft.

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